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Influence of Cooling Rate on the Enthalpy Relaxation and Fragility of a Metallic Glass

Raghavan, R and Murali, P and Ramamurty, U (2008) Influence of Cooling Rate on the Enthalpy Relaxation and Fragility of a Metallic Glass. In: Symposium on Materials Behavior - Far from Equilibrium, DEC 15-16, 2006, Bombay.

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Abstract

Structural relaxation behavior of a rapidly quenched (RQ) and a slowly cooled Pd40Cu30Ni10P20 metallic glass was investigated and compared. Differential scanning calorimetry was employed to monitor the relaxation enthalpies at the glass transition temperature, T-g , and the Kolrausch-Williams-Watts (KWW) stretched exponential function was used to describe its variation with annealing time. It was found that the rate of enthalpy recovery is higher in the ribbon, implying that the bulk is more resistant to relaxation at low temperatures of annealing. This was attributed to the possibility of cooling rate affecting the locations where the glasses get trapped within the potential energy landscape. The RQ process traps a larger amount of free volume, resulting in higher fragility, and in turn relaxes at the slightest thermal excitation (annealing). The slowly cooled bulk metallic glass (BMG), on the other hand, entraps lower free volume and has more short-range ordering, hence requiring a large amount of perturbation to access lower energy basins.

Item Type: Conference Paper
Additional Information: Copyright of this article belongs to The Minerals, Metals & Materials Society.
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 24 Mar 2010 07:52
Last Modified: 19 Sep 2010 05:58
URI: http://eprints.iisc.ernet.in/id/eprint/26487

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